Fast Ferry Modified to Launch Torpedoes

Tuesday, June 01, 2004

Gladding-Hearn Shipbuilding’s fast ferry building expertise has taken an unusual turn, with the testing of a new torpedo-launching system for the U.S. Navy. Systems Engineering Associates Corporation (SEA CORP) of Middletown, R.I., chartered Millennium, the 125-ft. Incat-designed high-speed passenger ferry owned by Rhode Island Fast Ferry and built by the Somerset, Mass., shipyard in 1998 in May, to test an experimental surface torpedo launching system under development by NAVSEA. The catamaran’s 37-knot light speed and open third deck were ideally suited to simulate launching from a destroyer or carrier deck.

Using their 3-D Finite Element Modeling (FEM) capability, the shipyard’s engineering staff designed a removable foundation to absorb the 12,000-pound reaction force, produced when launching a 750-pound simulated projectile. To facilitate the vessel’s quick return to ferry service, the shipyard imbedded a series of threaded inserts in the primary deck structure through the lightweight extruded aluminum decking.

“A 12,000 pound reaction force is relatively small when compared to the Millennium’s normal passenger load, but not trivial when you consider the light aluminum structure and small area over which it was spread,” explained Peter Duclos, the shipyard’s president director of business development. “The FEM quickly showed us the areas of highest stress and allowed us to efficiently design a cost-effective solution.”

The new launcher technology, which was developed jointly by the Naval Undersea Warfare Center (NUWC) and SEA CORP, uses multiple standard automotive auto bag inflators to provide the energy to launch payloads. “This technology makes possible for the first time a sealed and completely modular torpedo launch canister for surface warships, said NUWC engineer David Godfrey.

The launcher was tested in a secured section of Narragansett Bay in mid-May. The vessel returned immediately afterwards to scheduled ferry service between Quonset Point, R.I., and Martha’s Vineyard, Massachusetts